Agilent Technologies 4294A Service Manual download pdf (Page 181)

Chapter 12 181

Using LAN

Controlling the Agilent 4294A

1. Chapter Title

12. Using LAN 3. Chapter Title

4. Chapter Title

5. Chapter Title

Below are described subprograms corresponding to each step in Figure 12-6:

Startup

The subprogram corresponding to Startup is StartIt (Example 12-2). StartIt uses the version of

WinSock API entered into the part 1 of Figure 12-5 to start up and initialize WinSock API with the

WSAStartup function of WinSock API. This WSAStartup function must always be executed at the

start of WinSock. Parameters for this function are version No. (input) and startup information

(output).

Example 12-2 StartIt

Sub StartIt()

Dim StartUpInfo As WSAData

'Version 1.1 (1*256 + 1) = 257

'version 2.0 (2*256 + 0) = 512

'Get WinSock version

Sheets("Sheet1").Select

Range("C2").Select

version = ActiveCell.FormulaR1C1

'Initialize Winsock DLL

x = WSAStartup(version, StartUpInfo)

End Sub

Socket creation and connection

The subprogram corresponding to socket creation and connection is OpenSocket (Example 12-3).

OpenSocket establishes a connection to the socket of the port specified by PortNumber, an input

parameter, on a machine with the IP address specified by Hostname, an input parameter. Below are

described steps of OpenSocket:

In (1), the inet_aadr function of WinSock API is used to convert an IP address delimited by “.” to an

Internet address.

In (2), the socket function of WinSock API is used to create a new socket and acquire the descriptor

of this socket. If an error occurs during this operation, the function outputs a message and returns

processing to the main program. Parameters for the socket function are Address Family (input),

Socket Type (input) and Protocol No. (input).

In (3), a socket address is set. htons used at setting of the port No. is a WinSock API function that

converts a 2-byte integer from the Windows-type byte order (little endian) to the network byte order

(big endian).

In (4), the connect function of WinSock is used for connection to the 4294A. If an error occurs

during this operation, the function outputs a message and returns processing to the main program.

Parameters for the connect function are Socket Descriptor (input), Socket Address and Socket

Address Size (input).

Example 12-3 OpenSocket

Function OpenSocket(ByVal Hostname As String, ByVal PortNumber As Integer) As

Integer

Dim I_SocketAddress As sockaddr_in

Dim ipAddress As Long

ipAddress = inet_addr(Hostname) '...................(1)

'Create a new socket

socketId = socket(AF_INET, SOCK_STREAM, 0) '

If socketId = SOCKET_ERROR Then '

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Agilent Technologies 4294A Service Manual Page 181

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